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Case Report

Exp Neurobiol 2013; 22(3): 232-234

Published online September 30, 2013

© The Korean Society for Brain and Neural Sciences

A Case of Thyrotoxic Myopathy with Extreme Type 2 Fiber Predominance

Tae Jung Kim, Han Sang Lee, Je-Young Shin, Dong-Gun Kim, Sung-Min Kim, Jung-Joon Sung and Kwang-Woo Lee*

Department of Neurology, Seoul National University Hospital, Seoul 110-744, Korea

Correspondence to: *To whom correspondence should be addressed.
TEL: 82-2-2072-3215, FAX: 82-2-3672-7553


In hyperthyroidism, many patients had neuromuscular symptoms and clinical weakness correlated with free thyroxine (T4) concentrations. The common clinical symptoms of chronic thyrotoxic myopathy were characterized by progressive weakness in proximal muscles and atrophy. A 55-year old woman was visited our hospital with two years of progressive weakness of both legs. Physical examination showed diffuse enlargement of the thyroid gland, muscle atrophy and tachycardia. Motor examination showed proximal weakness in both legs. Serum creatine phosphokinase was normal and electromyography showed a myopathic pattern. Serum thyroxine (T4) was greatly increased and serum thyroid stimulating hormone was very low. Muscle biopsy showed mild atrophic change and type 2 fiber predominance. The patient's symptoms were improved during treatment with methimazole. Herein we report a case of thyrotoxic myopathy with extreme type 2 fiber predominance histologically.

Keywords: thyrotoxic myopathy, hyperthyroidism, type 2 fiber